In 2018, Lake Keowee was described as South Carolina's "most deadly body of water" in a chilling local news article.
At the time of writing, 32 people had died in a 25-year span.
Otim's former Forest team-mate Cash was quick to pay tribute, saying he "always brought a smile to everyone's face".
The midfielder had recently graduated from Xavier University - and is claimed to have been visiting friends in South Carolina.
After hearing the tragic news, Forest star Cash tweeted: "RIP del , can’t believe I’m writing this.
"Such a top lad who always brought a smile to everyone’s face when around him , RIP".
Nottingham Forest also tweeted, writing: "Rest in peace, Derrick.
"#NFFC are saddened to learn of the passing of former academy player Derrick Otim.
"The thoughts of everyone at the club go out to his friends and family at this tragic time."
Rest in peace, Derrick ❤️— Nottingham Forest FC (@NFFC) July 5, 2020
#NFFC are saddened to learn of the passing of former academy player Derrick Otim.
The thoughts of everyone at the club go out to his friends and family at this tragic time. pic.twitter.com/zqR5thSHlm